1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly, to a semiconductor device that switches operation modes based on the presence or absence of bonding.
2. Description of the Related Art
It is a common practice to form circuits for implementing different multiple functions on a substrate (chip) in advance, select a specific function that meets the user's request upon assembly into a semiconductor device, and customize the semiconductor device by activating a circuit that has the selected function. With this, a semiconductor device that fulfills users' individual requests can be manufactured while reducing the total manufacture cost by making a general-purpose chip.
U.S. Pat. No. 5,754,879 describes a technology of selecting any one of multiple operation modes based on whether or not an external terminal (power supply external terminal, ground external terminal, or reset external terminal) is bonded to an internal terminal (mode pad), which is provided on a chip for operation mode selection. This technology enables a semiconductor device to select an operation mode only based on the presence or absence of bonding without newly installing an external terminal through which special signals for operation mode selection are supplied.
Internal terminals through which signals are input from and output to the outside of a chip are placed along the perimeter of the chip. In a central area of the chip that is surrounded by the pads, various circuits are formed. The recent advancement in miniaturization and multi-layer wiring has made it possible to mount numerous circuits to a chip. However, a chip cannot have more circuits without an accompanying increase in the number of pads required to be placed along the perimeter of the chip and, for some products, the number of pads required to be placed along the perimeter of the chip determines the chip size.
The present inventor has recognized that, in a chip where various circuits for satisfying individual users' requests and mode pads for operation mode selection are mounted, adding a mode pad increases the chip size. Specifically, what is important is to keep the chip size from increasing while trying to meet requests of users as much as possible by mounting circuits that implement different multiple functions to the chip.